BENGHAZI, Libya — The long, brutal reign of Col. Moammar Gadhafi appeared to collapse Sunday as rebels swept into Tripoli, captured three of his sons and set off wild street celebrations in a capital that he’d ruled by fear for more than four decades, Libyan and NATO officials said.

With NATO bombings paving the way, rebel forces entered Tripoli with surprising ease and by early Monday controlled large swaths of the city. Gadhafi’s personal guard surrendered to rebel forces, and live television footage showed crowds of opposition supporters in Tripoli’s Green Square — the regime’s symbolic heart — unfurling the tricolor flag of pre-Gadhafi Libya and smashing the ruler’s portraits in scenes that were unthinkable just days ago.

“This is historic,” Amal Abdelrazk, a 42-year-old resident of downtown Tripoli’s Andalus Street, said by phone. “After 41 years, eight months and 27 days, we witness this moment….

“The whole thing is like a dream.”

As rebels partied in the streets, hailed “as the victors of war,” Abdelrazk said, rebel military spokesman Col. Ahmed Bani told McClatchy that his forces were hunting Gadhafi in and around Tripoli. Gadhafi’s whereabouts were unknown, but a U.S. official said, “We have no reason to believe (he) has left the country.”

Late Sunday Gadhafi made a brief audio statement on Libyan TV, sounding desperate as he called on individual tribes and cities to “take weapons” and defend “beautiful Tripoli."

"All the tribes, you must all march to Tripoli in order to defend and purify it,” he said, calling the rebels agents of Western powers. “Otherwise you will have no dignity; You will become slaves and servants in the hands of the imperialists.”